AMSTERDAM – Europol says 17 people have been arrested in an international crackdown on underground websites selling illegal drugs.

In a statement, the European policing agency said Friday that it coordinated raids a day earlier together with U.S. law enforcement agencies, who Thursday announced the arrest in San Francisco of a man accused of running the "Silk Road 2.0" online drug bazaar. Europol said that in addition to the Silk Road site, several other marketplaces were seized, netting $1 million (800,000 euros) in digital currency and $225,000 worth of cash and drugs.

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Silk Road and similar websites are not visible on the open Internet; they can only be accessed with special browsers that encrypt web traffic. Buyers and sellers trade using digital currencies, usually Bitcoin.